This invention relates generally to a computer-controlled method and apparatus for fabricating a three-dimensional (3-D) object and, in particular, to an improved method and apparatus for building a 3-D object directly from a computer-aided design of the object in a layer-by-layer fashion.
Solid freeform fabrication (SFF) or layer manufacturing (LM) is a new fabrication technology that builds an object of any complex shape layer by layer or point by point without using a pre-shaped tool (die or mold). This process begins with creating a Computer Aided Design (CAD) file to represent the geometry or drawing of a desired object. As a common practice, this CAD file is converted to a stereo lithography (.STL) format in which the exterior and interior surfaces of the object is approximated by a large number of triangular facets that are connected in a vertex-to-vertex manner. A triangular facet is represented by three vertex points each having three coordinate points: (x1,y1,z1), (x2,y2,z2), and (x3,y3,z3). A perpendicular unit vector (i,j,k) is also attached to each triangular facet to represent its normal for helping to differentiate between an exterior and an interior surface. This object image file is further sliced into a large number of thin layers with the contours of each layer being defined by a plurality of line segments connected to form polylines on an X-Y plane of a X-Y-Z orthogonal coordinate system. The layer data are converted to tool path data normally in terms of computer numerical control (CNC) codes such as G-codes and M-codes. These codes are then utilized to drive a fabrication tool for defining the desired areas of individual layers and stacking up the object layer by layer along the Z-direction.
This SFF technology enables direct translation of the CAD image data into a three-dimensional (3-D) object. The technology has enjoyed a broad array of applications such as verifying CAD database, evaluating design feasibility, testing part functionality, assessing aesthetics, checking ergonomics of design, aiding in tool and fixture design, creating conceptual models and sales/marketing tools, generating patterns for investment casting, reducing or eliminating engineering changes in production, and providing small production runs.
The SFF techniques may be divided into three major categories: layer-additive, layer-subtractive, and hybrid (combined layer-additive and subtractive). A layer additive process involves adding or depositing a material to form predetermined areas of a layer essentially point by point; but a multiplicity of points may be deposited at the same time in some techniques, such as of the multiple-nozzle inkjet-printing type. These predetermined areas together constitute a thin section of a 3-D object as defined by a CAD geometry. Successive layers are then deposited in a predetermined sequence with a layer being affixed to its adjacent layers for forming an integral 3-D, multi-layer object. A 3-D object, when sliced into a plurality of constituent layers or thin sections, may contain features that are not self-supporting and in need of a support structure during the object-building procedure. These features include isolated islands in a layer and overhangs. In these situations, additional steps of building the support structure, also on a layer-by-layer basis, will be required of a layer-additive technique. An example of a layer-additive technique is the fused deposition modeling (FDM) process as specified in U.S. Pat. No. 5,121,329 (issued on Jun. 9, 1992 to S. S. Crump).
A layer-subtractive process involves feeding a complete solid layer to the surface of a support platform and using a cutting tool (normally a laser) to cut off or somehow degrade the integrity of the un-wanted areas of this solid layer. The solid material in these un-wanted areas of a layer becomes a part of the support structure for subsequent layers. These un-wanted areas are hereinafter referred to as the xe2x80x9cnegative regionxe2x80x9d while the remaining areas that constitute a section of a 3-D object are referred to as the xe2x80x9cpositive regionxe2x80x9d. A second solid layer is then fed onto the first layer and bonded thereto. The same cutting tool is then used to cut off or degrade the material in the negative region of this second layer. These procedures are repeated successively until multiple layers are laminated to form a unitary object. After all layers have been completed, the unitary body (part block) is removed from the platform, and the excess material (in the negative regions) is removed to reveal the 3-D object. This xe2x80x9cdecubingxe2x80x9d procedure is known to be tedious and difficult to accomplish without damaging the object. An example of a layer subtractive technique is the well-known laminated object manufacturing (LOM), disclosed in U.S. Pat. No. 4,752,352 (Jun. 21, 1988 to M. Feygin), U.S. Pat. No. 5,354,414 (Oct. 11, 1994 to M. Feygin) and U.S. Pat. No. 5,637,175 (Jun. 10, 1997 to M. Feygin, et al).
A hybrid process involves both layer-additive and subtractive procedures. An example can be found with the Shape Deposition Manufacturing (SDM) process disclosed in U.S. Pat. No. 5,301,863 issued on Apr. 12, 1994 to Prinz and Weiss. The SDM-based fabrication system contains a material deposition station and a plurality of processing stations (for mask making, heat treating, packaging, complementary material deposition, shot peening, cleaning, shaping, sand-blasting, and inspection). The combined deposition-shaping procedures qualify the SDM as a hybrid layer manufacturing technique. In the SDM system, each processing station performs a separate function such that when the functions are performed in series, a layer of an object is produced and is prepared for the deposition of the next layer. This system requires an article transfer apparatus, a robot arm, to repetitively move the object-supporting platform and any layers formed thereon out of the deposition station into one or more of the processing stations before returning to the deposition station for building the next layer. These additional operations in the processing stations tend to shift the relative position of the object with respect to the object platform. Further, the transfer apparatus may not precisely bring the object to its exact previous position. Hence, the subsequent layer may be deposited on an incorrect spot, thereby compromising part accuracy. The more processing stations that the growing object has to go through, the higher the chances are for the part accuracy to be lost. Such a complex and complicated process necessarily makes the over-all fabrication equipment bulky, heavy, expensive, and difficult to maintain. The equipment also requires attended operation.
Another good example of layer-additive techniques is the 3-D printing technique (3D-P) developed at MIT; e.g., U.S. Pat. No. 5,204,055 (April 1993 to Sachs, et al.). This 3-D powder printing technique involves dispensing a layer of loose powders onto a support platform and using an ink jet to spray a computer-defined pattern of liquid binder onto a layer of uniform-composition powder. The binder serves to bond together those powder particles on those areas defined by this pattern. Those powder particles in the un-wanted regions remain loose or separated from one another and are removed at the end of the build process. Another layer of powder is spread over the preceding one, and the process is repeated. The xe2x80x9cgreenxe2x80x9d part made up of those bonded powder particles is separated from the loose powders when the process is completed. This procedure is followed by binder removal and the impregnation of the green part with a liquid material such as epoxy resin and metal melt. The loose powders tend to create a big mess inside the fabrication machine and adjacent areas. Such a machine may not be very suitable for use in an office environment.
This same drawback is true of the selected laser sintering or SLS technique (e.g., U.S. Pat. No. 4,863,538, Sep. 5, 1989 to C. Deckard) that involves spreading a full-layer of loose powder particles and uses a computer-controlled, high-power laser to partially melt these particles at predetermined spots. Commonly used powders include thermoplastic particles or thermoplastic-coated metal and ceramic particles. The procedures are repeated for subsequent layers, one layer at a time, according to the CAD data of the sliced-part geometry. The loose powder particles in each layer are allowed to stay as part of a support structure. The sintering process does not always fully melt the powder, but allows molten material to bridge between particles. Commercially available systems based on SLS are known to have several drawbacks. One problem is that long times are required to heat up and cool down the material chamber after building. The need to use a high power laser makes the SLS an expensive technique and unsuitable for use in an office environment.
In U.S. Pat. No. 5,514,232, issued May 7, 1996, Burns discloses a method and apparatus for automatic fabrication of a 3-D object from individual layers of fabrication material having a predetermined configuration. Each layer of fabrication material is first deposited on a carrier substrate in a deposition station. The fabrication material along with the substrate are then transferred to a stacker station. At this stacker station the individual layers are stacked together, with successive layers being affixed to each other and the substrate being removed after affixation. One advantage of this method is that the deposition station may permit deposition of layers with variable colors or material compositions. In real practice, however, transferring a delicate, not fully consolidated layer from one station to another would tend to shift the layer position and distort the layer shape. The removal of individual layers from their substrate also tends to inflict changes in layer shape and position with respect to a previous layer, leading to inaccuracy in the resulting part.
Lamination-based layer manufacturing (LM) techniques that involve transferring thin sections of a solid or powders are also disclosed in U.S. Pat. No. 5,088,047 (Feb. 11, 1992 to D. Bynun) and U.S. Pat. No. 5,593,531 (Jan. 14, 1997 to S. M. Penn). Lamination-based LM techniques that require radiation curing of solid sheet materials layer by layer can be found in U.S. Pat. No. 5,174,843 (Dec. 29, 1992 to M. Natter), U.S. Pat. No. 5,352,310 (Oct. 4, 1994 to M. Natter), and U.S. Pat. No. 5,183,598 (Feb. 2, 1993 to J-L Helle, et al.). Disclosed in this latter patent (U.S. Pat. No. 5,183,598) is a process that includes preparing thin non-porous sheets of a fiber- or screen-reinforced matrix material. In these composite sheets, the matrix material exhibits the feature that its solubility in a specific solvent can be changed when the material is exposed to a specific radiation. Selected areas of individual sheets are radiated to reduce the solubility. The un-irradiated portion (the negative region) of individual layers remains soluble in the solvent. The stack of sheets are affixed together to form an integral body, which is immersed in the solvent that causes the desired object to appear. This process exhibits the following shortcomings:
1). A solvent is used, which can pose a health hazard.
2). A radiation source (e.g., a laser beam) is required. High energy radiation sources and their handling equipment (for reflecting, focusing, etc) are expensive. Furthermore, they are not welcome in an office environment.
3). It is difficult for a radiation to penetrate a solid sheet with an embedded screen or fibers. These reinforcement fibers or screen would tend to scatter or absorb the imposing radiation, making the solubility changes in the matrix material non-homogeneous. In particular, the material near the bottom of a sheet, opposite the radiation source, may not be properly cured and can remain soluble at the end of the layer-stacking procedure. When immersed in a solvent, this under-cured portion of the material would be dissolved, leaving behind a disintegrated structure.
4). This process makes use of uniform-composition sheets of solid materials and, hence, is not amenable to the fabrication of layers with material compositions varying from point to point and from layer to layer. For instance, this process does not allow for the fabrication of a multi-color object in which a different layer has a different color or a different portion of a layer has a different color pattern.
5). When a screen is used as the reinforcement, the screen in the negative region is difficult to get dissolved in the solvent particularly if this screen is made of metal or ceramic materials. A strong acid is needed in dissolving a metal screen, as suggested in U.S. Pat. No. 5,183,598.
Due to the specific solidification mechanisms employed, many LM techniques are limited to producing parts from specific polymers. For instance, Stereo Lithography and Solid Ground Curing (SGC) rely on ultraviolet (UV) light induced curing of photo-curable polymers such as acrylate and epoxy resins.
The above discussion has indicated that all prior-art layer manufacturing techniques have serious drawbacks that have prevented them from being widely implemented.
Therefore, an object of the present invention is to provide an improved layer-additive method and apparatus for producing a 3-D object in an office environment.
Another object of the present invention is to provide a computer-controlled method and apparatus for producing a multi-material or multi-color part on a layer-by-layer basis.
It is a further object of this invention to provide a computer-controlled composite building method that does not require heavy and expensive equipment.
It is another object of this invention to provide a method and apparatus for building a CAD-defined object in which the support structure is readily provided during the layer-adding procedure and is easily removed at the completion of this procedure.
Still another object of this invention is to provide a layer manufacturing technique that places minimal constraint on the range of materials that can be used in the fabrication of a 3-D object.
The Method
The objects of the invention are realized by a method and related apparatus for fabricating a three-dimensional object on a layer-by-layer basis. Basically, the method includes, in combination, the following steps:
(a) setting up a work surface that lies substantially parallel to an X-Y plane of an X-Y-Z Cartesian coordinate system defined by three mutually orthogonal X-, Y- and Z-axes;
(b) feeding a first porous solid preform layer to the work surface; the pore content being preferably in the range of 30% to 70% and further preferably in the range of 40-60%;
(c) using dispensing devices to dispense a first pore-filling material onto predetermined areas of the first porous preform layer to at least partially fill in pores in these predetermined areas for the purpose of hardening these areas and forming the first section of the 3-D object; these predetermined areas, in combination, constituting the geometry of this first section and are referred to collectively as the xe2x80x9cpositive regionxe2x80x9d;
(d) feeding a second porous preform layer onto the first layer, dispensing a second pore-filling material onto predetermined areas of the second layer for hardening these areas and forming the second section of the 3-D object;
(e) repeating the operations from (b) to (d) to stack up successive preform layers along the Z-direction of the X-Y-Z coordinate system for forming multiple layers of the object with the remaining un-hardened areas (negative region) of individual layers staying as a support structure;
(f) providing means to sequentially or simultaneously affix successive layers together to form a unitary body; and
(g) removing the support structure by exposing the un-hardened areas of this unitary body to a support-collapsing environment, causing the 3-D object to appear.
In this method, the porous solid preform layers may contain a reinforcement composition selected from the group consisting of short fiber, long fiber, whisker, spherical particle, ellipsoidal particle, flake, small platelet, small ribbon, disc, particulate of any other shape, or a combination thereof. In this method, the porous preform layers preferably comprise a watersoluble material composition and the support-collapsing environment comprises water. Specifically, individual short fibers and/or reinforcement particles may be bonded together at their points of contact by a water soluble glue (e.g., polyvinyl alcohol-based glue), leaving behind pores interspersed with those fibers or particles. These otherwise isolated fibers and particles, when glued together, will make a porous solid layer that is rigid enough to be handled by the preform feeder in the invented fabricator apparatus. In the predetermined areas (positive region), the fibers and particles are coated, covered, or otherwise protected by the deposited pore-filling materials. The material in this positive region will remain essentially intact while the fibers/particles in the support structure or negative region will be separated/isolated due to the glue being dissolved in water. This step will allow the support structure to collapse, thereby revealing the desired 3-D object.
Alternatively, the support structure may be made to contain a material composition with a melting point lower than the melting or decomposition temperature of the hardened areas (positive region). In this case, the unitary body may be subjected to a support-collapsing temperature (Tsc) higher than the melting point of this glue material (e.g., poly ethylene oxide with a Tm=63xc2x0 C.) and lower than either the melting point of the pore-filling material (e.g., polyethylene with a Tm=130xc2x0 C.) or the degradation temperature of a cured thermoset resin (e.g., much higher than 250xc2x0 C. for epoxy). In this manner, the support-collapsing environment comprises a high temperature environment to melt out the low-melting composition (glue) for readily collapsing the support structure to reveal the 3-D structure.
There are available many thermosetting resins which, upon curing, harden the preform layers. Examples are epoxy, un-saturated polyester, phenolic, and polyimide resins. There are also a wide range of thermoplastic materials that can be chosen from for use as a pore-filling material. These materials may be heated above their glass transition temperatures, Tg (if they are amorphous polymers such as polystyrene, poly carbonate, and acrylonitrile-butadine-styrene or ABS) or their melting points, Tm (if they are semi-crystalline polymers such as polypropylene and nylon). These thermoplastic melts can then be dispensed and deposited to partially fill the pores to coat, cover, or protect the underling fibers/particles. These melts, upon cooling below their Tg or Tm, will solidify and harden the preform layers. Although not a preferred approach, a thermoplastic polymer may be dissolved in a solvent to form a solution. This solution may be dispensed and deposited as a pore-filling material. Once, the solvent is removed (e.g., under the action of a ventilation system), the polymer will precipitate out to cover, coat, or protect the fibers/particles and harden the preform layers.
The porous preform layers may be made to contain a hardenable ingredient (e.g., an epoxy resin) and the pore-filling material comprises a chemical composition (e.g., a curing agent) which reacts with this ingredient to form a solid product (e.g., a cross-linked or cured resin) for hardening the preform layers. A wide range of such two-part resins are available commercially.
In the presently invented method, the dispensing means may be selected from the group of devices consisting of an inkjet printhead, gear pump, positive displacement pump, air pump, metering pump, extrusion screw, solenoid valve, thermal sprayer, and combinations thereof. The dispensing devices may be equipped with multiple nozzles or multiple discharge orifices for dispensing a plurality of material compositions.
A convenient way of feeding preform layers one sheet at a time is using a mechanism involving motor-driven rollers that are commonly used in a copier, fax machine, graphic plotter, or desk-top printer.
The operation of using dispensing means to dispense a pore-filling material onto predetermined areas of a porous preform layer preferably include the steps of (1) positioning the dispensing means at a predetermined initial distance from the work surface; (2) operating and moving the dispensing means relative to the work surface along selected directions in the X-Y plane to dispense and deposit the pore-filling material to the predetermined areas; (3) moving the dispensing means away from the work surface along the Z-axis direction by a predetermined distance to allow for the building of a subsequent layer. The movement of the dispensing devices relative to the work surface may be carried out by using any motor-driven linear motion devices, gantry table, or robotic arms which are all widely available commercially.
The moving and dispensing operations of the dispensing means are preferably conducted under the control of a computer. This can be accomplished by (1) first creating a geometry of the three-dimensional object on a computer with the geometry including a plurality of data points defining the object (a procedure equivalent to computer-aided design), (2) generating programmed signals corresponding to each of the data points in a predetermined sequence; and (3) moving the dispensing means and the work surface relative to each other in response to these programmed signals. These signals may be prescribed in accordance with the G-codes and M-codes that are commonly used in computer numerical control (CNC) machinery industry.
In order to produce a multi-material 3-D object in which the material composition or color can vary from point to point, the presently invented method may further comprise the steps of (1) creating a geometry of the 3-D object on a computer with the geometry including a plurality of data points defining the object; each of the data points being coded with a selected material composition, (2) generating programmed signals corresponding to each of the data points in a predetermined sequence; and (3) operating the dispensing means in response to the programmed signals to dispense and deposit selected material compositions while the dispensing means and the work surface are moved relative to each other in response to these programmed signals in the predetermined sequence.
To further ensure the part accuracy and compensate for the potential variations in part dimensions (thickness, in particular), the present method may be executed under the assistance of dimension sensors. These sensors may be used to periodically measure the dimensions of the object being built while a computer is used to determine the thickness and outline of individual layers intermittently in accordance with a computer aided design representation of the object. The computing step includes operating the computer to calculate a first set of logical layers with specific thickness and outline for each layer and then periodically re-calculate another set of logical layers after periodically comparing the dimension data acquired by the sensor with the computer aided design representation in an adaptive manner.
The Apparatus
Another embodiment of this invention is a solid freeform fabrication apparatus for automated fabrication of a 3-D object. This apparatus includes: (a) a work surface to support the object while being built; (b) a feeder for feeding successive porous solid preform layers onto the work surface one layer at a time; (c) dispensing devices for dispensing at least a pore-filling material onto the porous solid preform layers; (d) motion devices coupled to the work surface and the dispensing devices for moving the dispensing devices and the work surface relative to each other in a plane defined by the X- and Y-directions and in the Z direction orthogonal to the X-Y plane in an X-Y-Z coordinate system to dispense at least a pore-filling material onto the porous preform layers for forming this 3-D object.
In this apparatus, the dispensing devices may include a device selected from the group consisting of an ink jet print-head with thermally activated actuator means, an ink jet print-head with piezo-electrically activated actuator means, an air gun with compressed air-powered actuator means, a gear pump, a positive displacement pump, a metering pump, an extrusion screw, a solenoid valve, and a thermal sprayer. The function of such a device is to deliver, on demand, droplets or strands of a solidifying liquid to enter the pores in selected areas of a preform layer; these selected areas defining a cross section of the 3-D object being built. A dispensing device may feature a plurality of nozzles each with at least one discharge orifice of a predetermined size for dispensing at least one pore-filling material. When a multiplicity of materials is dispensed and deposited, a multi-material or composite object is built.
Preferably, the apparatus further includes a consolidating device (e.g., a heated roller) coupled to the motion devices for compacting, hardening, or consolidating the preform layers along with the dispensed pore-filling material. Once a new layer of preform is fed into the build zone above the work surface, a heated roller may be activated to roll over this new layer to help affix this layer to a preceding layer. Alternatively, the roller may be used intermittently after a selected number of layers are stacked up together to help consolidate these layers.
In order to automate the object-fabricating process, the present apparatus is equipped with a computer-aided design computer and supporting software programs operative to (a) create a three-dimensional geometry of the 3-D object, (b) convert this geometry into a plurality of data points defining the object, and (c) generate programmed signals corresponding to each of the data points in a predetermined sequence. The apparatus also includes a three-dimensional motion controller electronically linked to the computer and the motion devices. The motion controller is operated to actuate the motion devices in response to the programmed signals for each of the data points received from the computer.
The apparatus preferably includes dimension sensors that are electronically linked to the computer. The sensors periodically provide layer dimension data to the computer. In the mean time, the supporting software programs in the computer act to perform adaptive layer slicing to periodically create a new set of layer data, including the data points defining the object, in accordance with the layer dimension data acquired by the sensors means. New sets of programmed signals corresponding to each of the new data points are generated in a predetermined sequence.
The object-supporting work surface or platform is generally flat and is located at a predetermined initial distance from (but in close, working proximity to) the discharge orifices of the dispensing devices to receive discharged materials therefrom. The motion devices are coupled to the work surface and the dispensing devices for moving the dispensing devices and the work surface relative to each other in an X-Y plane defined by first and second directions (X- and Y-directions) and in a third direction (Z-direction) orthogonal to the X-Y plane to deposit the pore-filling materials to form a 3-D object. The motion devices are preferably controlled by a computer system for positioning the dispensing devices with respect to the platform in accordance with a CAD-generated data file representing the object. Further preferably, the same computer is used to regulate the operations of the material dispensing devices in such a fashion that pore-filling materials are dispensed in predetermined sequences with predetermined proportions at predetermined rates.
Specifically, the motion devices are responsive to a CAD-defined data file which is created to represent the 3-D preform shape to be built. A geometry (drawing) of the object is first created in a CAD computer. The geometry is then sectioned into a desired number of layers with each layer being comprised of a plurality of data points. These layer data are then converted to machine control languages that can be used to drive the operation of the motion devices and dispensing devices. These motion devices operate to provide relative translational motion of the material dispensing devices with respect to the work surface in a horizontal direction within the X-Y plane. The motion devices further provide relative movements vertically in the Z-direction, each time by a predetermined layer thickness.
The chemical compositions in the pore-filling materials may be comprised of, but is not limited to, the following materials including various adhesives, waxes, solutions containing a thermoplastic polymer dissolved in a solvent, thermosetting resins, sol-gel mixtures, and combinations thereof. The compositions may also include combinations containing dissimilar materials added to impart a desired electrical, structural, or other functional characteristic to the material. One presently preferred pore-filling liquid material comprises a hot melt adhesive that exhibits a high adhesion to the material in previously or subsequently deposited layers.
Advantages of the Invention
The process and apparatus of this invention have several features, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention as expressed by the claims which follow, its more prominent features will now be discussed briefly. After considering this brief discussion, and particularly after reading the section entitled xe2x80x9cDESCRIPTION OF THE PREFERRED EMBODIMENTSxe2x80x9d one will understand how the features of this invention offer its advantages, which include:
(1) The present invention provides a unique and novel method for producing a three-dimensional object on a layer-by-layer basis under the control of a computer. This method does not require the utilization of a pre-shaped mold or tooling.
(2) Most of the layer manufacturing methods, including powder-based techniques such as 3-D printing (3D-P) and selective laser sintering (SLS), are normally limited to the fabrication of an object with a uniform material composition. The non-porous solid layer lamination technique disclosed in U.S. Pat. No. 5,183,598 (Feb. 2, 1993 to J-L Helle, et al.) suffers the same drawback. In contrast, the presently invented method with a plurality of discharge orifices readily allows the fabrication of a part having a spatially controlled material composition comprising two or more distinct types of pore-filling materials. This method offers an opportunity to impart desirable material composition patterns to an object, making it possible to produce functional materials including functionally gradient composites.
(3) The presently invented method provides a computer-controlled process which places minimal constraint on the variety of materials that can be processed. In the present method, the pore-filling materials may be selected from a broad array of materials including various organic and inorganic substances and their mixtures.
(4) The present method provides an adaptive layer-slicing approach and a thickness sensor to allow for in-process correction of any layer thickness variation (discussed later). The present invention, therefore, offers a preferred method of layer manufacturing when part accuracy is a desirable feature.
(5) The method can be embodied using simple and inexpensive mechanisms, so that the fabricator apparatus can be relatively small, light, inexpensive and easy to maintain.
(6) In the present method, a support structure naturally exists when a new preform layer is fed onto a preceding layer. No additional tool is needed to build a support structure. This is in contrast to most of the prior-art layer-additive techniques that require a separate tool to build a support structure also layer by layer, thereby slowing down the part-building process. Furthermore, with a 50% porosity level in a layer, the remaining 50% is already in a solid state. The dispensing devices only have to dispense the pore-filling materials to fill up to 50% of the layer volume, resulting in a further time saving by a factor of two.
(7) In contrast to other layer-subtractive techniques (e.g., LOM) in which the removal of excess materials used as a support structure is difficult to accomplish, the present method readily allows for easy removal of the support structure; e.g., by simply immersing the unitary 3-D body to a water bath or heating the body to a temperature slightly higher than the melting point of the glue or adhesive material in the support structure.